Through its various metabolites, vitamin A, retinol, controls essential physiological functions. Both naturally occurring metabolites and retinoid analogues have shown effectiveness in many clinical settings that include skin diseases and cancer, and in animal models of human conditions affecting vision. Retinoid therapies have demonstrated clinical efficacy as treatments for many debilitating diseases.
Typically, retinoids are complexed with soluble proteins that protect them. These reactive compounds are bound by a number of retinoid-binding proteins, and are rarely freely solubilized from membranes. Protection of retinoids also stems from their ability to cluster when esterified by long-chain fatty acids, and undergo storage in lipid-like droplets in the liver or as retinosomes in the eye. Evidence that esterification of retinol and retinol-based drugs within target tissues provides one of the most efficient means to improve the absorption and to reduce the toxicity associated with pharmacological doses of retinoids. Currently, there are few treatments for retinoid deficiency. Thus, there is a need for compositions and methods of restoring or stabilizing photoreceptor function and ameliorating the effects of deficient levels of endogenous retinoids.